The present invention relates to tandem trailer assemblies wherein trailers are pulled by a single truck tractor, and the difficulties involved in backing up the same.
The use of tandem trailers has become increasingly popular in recent years. The tandem arrangement permits a single truck to double its hauling capacity which feature is particularly advantageous in the moving industry. For instance, it is often desirable to move furniture in one trailer and move an automobile in a second trailer whereas in the past the automobile had to either be driven or towed behind the first trailer.
In operation, the first trailer is an integral truck cab assembly or is connected to the tractor using a fifth wheel and kingpin arrangement commonly known in the art. The second trailer is conventionally attached to the first trailer using a dolly carrying another fifth wheel assembly. These arrangements can provide pivot points between the tractor and the first trailer, between the first trailer and the dolly, and between the second trailer and the dolly. This arrangement does not significantly increase the cost to pull the two trailers and there is little or no loss in maneuverability so long as the tractor and trailers are traveling in a forward direction.
A problem occurs, however, when the driver of the tractor desires to back up the trailer assembly such as when delivering or picking up a load. The trailers must be disconnected from one another and separately backed up. This is due to the arrangement of the pivot points. While this arrangement is advantageous as to maneuverability, it is unsuitable for backing up the assembly because of the unmanagability of the pivot points. Conceivably the trailers can be disconnected and individually reversed and positioned, but this process obviously is time consuming and thus expensive.
Prior art devices are known which limit the pivotal movement of the converter dolly in relation to the first trailer. For instance, commonly assigned U.S. Pat. No. 5,098,115 to Haire et al. proposes such limiting means. Specifically, Haire et al. proposes a converter dolly comprising a fifth wheel which carries locking means including pins moveable between a retracted, inactive position for permitting pivotal movement of the second trailer during forward motion and an extended, active position for engagement with the second trailer to restrain the second trailer against pivotal movement during the backing up of the trailer assembly. During the backing up procedure, only two pivot points are unrestrained (i.e., between the tractor and the first trailer and between the first trailer and the converter dolly).
It is an object of this invention to provide a converter dolly which obviates the need to disconnect the trailers to back-up the assembly.
Another object of this invention is to provide a trailer assembly which is easily maneuverable either in the forward or reverse motion.
A further object of this invention is to provide a converter dolly which is operator friendly and which exhibits safety features.